Long period sea waves along the coast of Tagonoura shich were observed by a long period wave meter for about two years, from May 1968 to March 1970, are reported.
　The results of the observation are summarized as follows.
　1)The long period waves appear when a typhoon or a depressure passes the offshore of the Suruga bay taking the course of NE direction.
　2)Predominant wave period is 80～90 sec and 40 sec.
　3)The wave height of the long period waves is seemed to be about one-tenth of significant wave height.
　4)The maximum wave, 50 cm in height and 80 sec in period, who observed on 26the of July 1968.